Metal, ammonium nitrate explosive compositions containing chlorinated hydrocarbons



United States Patent METAL, AMMONIUM NITRATE EXPLOSIVE COM- POSITIONS CONTAINING CHLORINATED HY- DROCARBONS John E. Wyman, Stoneham, and Stanley F. Bedell, Andover, Mass., assignors to Monsanto Company, a corporation of Delaware No Drawing. Filed Mar. 23, 1964, Ser. No. 354,136

-' 8 Claims. (Cl. 1492) This invention relates .to explosive compositions and particularly to explosive compositions containing granular ammonium nitrate in predominate proportions.

Ammonium nitrate has been used as the principal component in explosives for many years. Although this material is a relatively strong oxidizing agent, it is not readily detonatab-le. Therefore, ammonium nitrate explosive compositions or blasting agents usually contain ammonium nitrate in uniform intimate mixtures with various fuels and sensitizers which in themselves are preferably nonexplosive. In spite of the large number of ammonium nitrate compositions that has been developed, considerable difl-lculty has been encountered in obtaining an ammonium nitrate explosive having adequate power, high velocity, controllable sensitivity, stability, economy and ease of preparation. Also no completely satisfactory ammonium nitrate blasting agent that could be safely handled and transported while being capable of reliable detonation in relative small diameter bore holes has been heretofore developed. Thus, in using substantially all of the ammonium nitrate blasting agents available prior to the advent of the present invention, reliance was necessarily made upon highly sensitive material or upon inordinately large diameter bore holes to insure self-propagation at a satisfactorily high rate of detonation.

It is, there :fore, an object of this invention to provide an ammonium nitrate explosive composition or blasting agent overcoming the disadvantages of the prior art. A further object of this invention is to provide improved ammonium nitrate explosive compositions Whose sensitivity can be readily modified over a large range by minor formulation modification. A more specific object of this invention is to provide a cap-insensitive ammonium nitrate blasting agent that will detonate and propagate in small diameter charges.

The above and other objects. are accomplished in accordance with this invention, generally speaking, by the formulation of explosive compositions containing granular ammonium nitrate, granule-s of aluminum, magnesium or aluminum-magnesium alloys and a liquid hydrocarbon at least a portion of the hydrocarbon content being chlorinated. More specifically, the present invention is directed to explosive compositions or blasting agents containing prilled ammonium nitrate, relatively coarse granules of aluminum, magnesium and alloys of these metals and a chlorinated hydrocarbon. A liquid hydrocarbon can be added to such formulation to render them oxygen balanced.

Although ammonium nitrate has been previously sensitized with various metals and also with chlorinated hydrocarbons, it has now been found that when these two components are employed in well-defined ratios as described hereinafter they have a synergistic effect on the sensitization of the ammonium nitrate. A similar synergistic effect has been found in mixtures of a chlorinated hydrocan vary somewhat but must be maintained within welldefined limits to insure the advantageous results of the present invention. Thus, the present compositions must be maintained within the following approximate ranges:

Percent Ammonium nitrate -95 Aluminum, magnesium and allows thereof 1-6 Chlorinated hydrocarbon 2.5-12 Liquid hydrocarbon 0-6 When the ammonium nitrate content exceeds about the resulting compositions .are exceedingly insensitive to detonation, whereas compositions containing less than about 85% ammonium nitrate are quite sensitive and, therefore, dangerous to transport. Likewise, the utilization of more than about 6% aluminum in such compositions rendered them unduly sensitive and less than about 1% aluminum has no significant effect. The chlorinated hydrocarbon must be present in amounts of at least 2.5% to realize the beneficial synergistic action with the light metal employed. Amounts of the liquid hydrocarbon in excess of about 12% act merely as a diluent. A non-chlorinated liquid hydrocarbon is employed in amounts up to about 6% to provide the necessary oxygen balance.

The ammonium nitrate employed is generally prilled fertilizer grade ammonium nitrate. These prills can be either coated or uncoated and are generally of a size between about 8 and 20 mesh (US. Standard Sieve Series). When coated are employed, they are provided with the usual coating of up to about 3% of diatomaceous earth, clay, kaolin or the like. In order to increase the density of the charge when desired, up to about one-half of the ammonium nitrate prills can be ground sufiiciently fine to pass through a 60 mesh screen.

The aluminum or magnesium employed in these formulations differs significantly from the so-called explosive and flake-paint grades of aluminum which are exceedingly finely-divided, readily oxidizable and dangerous to handle. These metals are present in the form of relatively coar-st and more or less spherical granules .With about 90% of the granules being within the size range of 40 to 200 mesh (U.S. Standard Sieve Series). A typical screen analysis range of aluminum alloys particularly well suited for the purposes of the present invention is as follows.

Size range: Wt. percent +30 0-5 30 +40 5-15 -40 +50 20-35 -50 +80 25-50 80 515 -100 +200 24 200 0-5 The aluminum or magnesium granules employed need not be pure but can contain small insignificant amounts of other materials. For example, one aluminum composition satisfactory for the present purposes contains about 1% lead, about 0.4% iron and about 0.1% silicon in addition to the aluminum.

The chlorinated hydrocarbon used in preparing the formulations under consideration can be either aromatic 1 or aliphatic with one or more chlorines. However, in the interest of stability, it is preferred that these compounds contain no ethylenic unsaturation. Aside from this, the particular chemical structure of the chlorinated hydrocarbon is not significant. It is only necessary that these chlorinated compounds are not readily hydrolyzable and that they are stable, inert and unreactive with the other components at the maximum temperatures, say about C. that may be encountered in storage and preparation. To facilitate uniform distribution of the chlorinated hydrocarbon with the other components, it is preferred that the chlorinated hydrocarbon be liquid or readily liquefiable. In any event it must have a melting point not greatly in excess of about 150 C. so as to avoid any hazardous mixing operations. Although, =o-dichlorobenzene is the preferred chlorinated hydro-- carbon, it can be replaced in whole or part with other chlorinated componds having the above characteristics. Additional representative chlorinated hydrocarbons that can be employed include benzotrichloride, chlorokerosene, ethylene dichloride, dichloropentanes, tetrachloroethane, tetrachloroethylene, carbon tetrachloride, trichlorobenzene, o-nitrochlorobenzene, 1,2,3-trichloropropane, 1,2, 4,5-tetrachlorobenzene and the like. These compounds can be used singly or in any combination.

The present invention and the manner in which it achieves its advantageous results will be more readily understood by reference to the following specific illustrative embodiments thereof. In these examples and throughout the specification, all proportions are expressed in parts by weight unless otherwise stated.

EXAMPLE 1 About 5355 parts of a prilled ammonium nitrate and about 3570 parts of ammonium nitrate prills ground to pass through a 60 mesh screen were uniformly mixed with about 400 parts of o-dichlorobenzene, about 275 parts of N0. 2 fuel oil and about 400 parts of coarse granular aluminum. The aluminum granules were sufiiciently coarse that substantially all of them were retained on a 100 mesh screen. The resultant mixture was then loaded into tubular cardboard containers having an inside diameter of approximately 2 inches and a length of about 18 inches. The material thus charged had an approximate density of 1.15 pounds per cubic foot. The tubular cartridges loaded with this preferred blasting agent were then arranged in a column about 4.5 feet long. This charge Was cap-insensitive, that is incapable of being initiated with a No. 8 blasting cap. However, it was readily detonated with five No. 8 caps in contact with one end of the charge. When thus initiated, the charge propagated throughout its entire length at a detonation rate of approximately 8300 feet per second.

Thus the synergistic sensitizing effect of the aluminum and -o-dichlorobenzene results in an explosive which is self-propagating in small diameter charges even when unconfined. Since the detonation rate is at least in part dependent upon the degree of confinement, it will be readily appreciated that much higher velocities are obtained in bore holes.

A number of other compositions within the scope of the present invention were prepared, charged and initiated in like manner. The approximate compositions and the sensitivity of these mixtures are set forth below in tabular form.

Table 1 Composition, Percent by Weight Sensi- Examplc N0. tivity DCB F.O. Al

umeqqmcamencneme-ax KOWIONNNMWOJWWN cnwmwtowmmwwmw In each or" these examples, approximately 60% of ammonium nitrate was in prilled form, whereas the remainder was ground sufiiciently fine to pass through a 60 mesh screen. In the above table, AN designates ammonium nitrate; DCB, o-dichlorobenzene; F.O., fuel oil; and the sensitivity value indicates the minimum number of No. 8 caps required for self-propagating initiation.

Another series of similar compositions differing primarily in the exclusion of the ground ammonium nitrate prills was prepared to further illustrate the present in vention. These were formulated and tested in the manner described above. Their compositions and sensitivities are set forth below.

Table II Example No.

AN DCB F.O. Al

EXAMPLE 26 In a manner substantially identical to that described above, a composition containing about 87.62% prilled ammonium nitrate and about 12.38% o-dichlorobenzene was prepared. In this composition the aluminum was completely replaced and in its stead about 1.25% of ferric acetyl acetonate was used. This composition was charged into two inch diameter cardboard tubes in the manner as described above and the tubes formed into a blasting column about 4.5 feet long. The composition thus prepared was cap-insensitive but readily detonated by ten No. 8 blasting caps. The composition was self-propagating throughout the entire length of the column and had a detonation velocity of about 6100 feet per second.

While the above examples are directed specifically to preferred embodiments of the present invention, it is readily appreciated that various modifications thereof will suggest themselves to those skilled in the art, for example, the ammonium nitrate employed can be prilled granular or ground and mixtures of these various types. Also the ammonium nitrate can contain anti-setting and dimensionally stabilizing agents, such as magnesium nitrate, arylalkyl sulfonates, amines, acid Magenta and the like. In addition minor amounts of various conventional explosive components can be incorporated into the compositions of the invention.

While this invention has been described with respect to various specific examples and embodiments, it is understood that the invention is not limited thereto and that it can be variously practiced within the scope of the following claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An explosive composition comprising a predominant proportion of prilled ammonium nitrate, granules of a metal selected from the group consisting of magnesium and aluminum, said granules being Within a size range of 40 to 200 mesh and a liquid hydrocarbon, at least a portion of the hydrocarbon being chlorinated, the chlorinated hydrocarbon being free of ethylenic unsaturation, stable, inert and unreactive at temperatures below about C.

2. An explosive composition comprising a predominant proportion of granular ammonium nitrate, granules of a metal selected from the group consisting of aluminum and magnesium, said granules being in the size range of from 40 to 200 mesh, a chlorinated hydrocarbon and a liquid hydrocarbon oil, the chlorinated hydrocarbon being free of ethylenic unsaturation, stable, inert and unreactive at temperatures below about 150 C.

3. An explosive composition in accordance with claim 2 wherein at least a portion of the metallic granules are replaced with ferric acetylacetonate.

4. An explosive composition comprising a predominant proportion of granular ammonium nitrate, granules of a metal selected from the group consisting of aluminum and magnesium, the major portion of said granules being .sufiiciently large to be retained on a 200 mesh screen and a chlorinated hydrocarbon, said composition being substantially oxygen balanced with a liquid hydrocarbon oil, the chlorinated hydrocarbon being free of ethylenic unsaturation, stable, inert and unreactive at temperatures below about 150 C.

5. An explosive composition comprising between about 85% and about 95% granular ammonium nitrate, between about 1% and about 6% granules of a metal selected from the group consisting of aluminum and magnesium, the major portion of said granules having a size range of 40 to 200 mesh, between about 2.5% and about 12% of a chlorinated hydrocarbon and the balance a liquid hydrocartbon oil, the chlorinated hydrocarbon being free of ethylenic unsaturation, stable, inert and unreactive at temperatures below about 150 C.

6. An explosive composition in accordance with claim 5 wherein at least one-half of the ammonium nitrate is prilled and the balance is ground.

7. An explosive composition comprising about 89.25% granular ammonium nitrate, about 4% granules of a metal selected from the group consisting of aluminum and magnesium, the major portion of said granules having a size within the range of to 200 mesh, about 4% odichlorobenzene and about 2.75% liquid hydrocarbon oil.

8. An explosive composition in accordance with claim 7 wherein at least one-half of the ammonium nitrate is prilled and the balance is ground.

References Cited by the Examiner UNITED STATES PATENTS 1,547,076 7/1925 Staudinger l4987 3,010,815 11/1961 Pierce et al 14922 3,027,283 3/ 1962 Bice 14960 X 3,156,595 11/1964 Camp et a1. 14987 3,163,113 12/1964 Davis et a1 149--87 X BENJAMIN R. PADGETT,

Acting Primary Examiner. 

1. AN EXPLOSIVE COMPOSITION COMPRISING A PREDOMINANT PROPORTION OF PRILLED AMMONIUM NITRATE, GRANULES OF A METAL SELECTED FROM THE GROUP CONSISTING OF MAGNESIUM AND ALUMINUM, SAID GRANULES BEING WITHIN A SIZE RANGE OF 40 TO 200 MESH AND A LIQUID HYDROCARBON, AT LEAST A PORTION OF THE HYDROCARBON BEING CHLORINATED, THE CHLORINATED HYDROCARBON BEING FREE OF ETHYLENIC UNSATURATION, STABLE, INERT AND UNREACTIVE AT TEMPERATURES BELOW ABOUT 150* C. 